Propylene oxide is an important industrial chemical intermediate. Propylene oxide may be produced by oxidation of propylene with an oxidant such as hydrogen peroxide (U.S. Pat. Nos. 4,833,260, 5,753,576, and 7,442,817), or by direct oxidation of propylene with oxygen and hydrogen in a solvent in the presence of a catalyst (U.S. Pat. Nos. 7,138,535, 7,238,817, 7,279,145, and 5,973,171). These processes are often carried out in a slurry phase and the solid catalyst is separated from the liquid and/gas reactor effluent by filtration or centrifugation, which may occur in the reactor or outside the reactor, see, e.g., U.S. Pat. No. 7,084,284.
U.S. Pat. No. 6,884,898 teaches a continuous propylene oxide production process comprising reacting propylene with molecular oxygen and hydrogen in the presence of a solvent having a boiling point of at least 130° C. and a solid noble metal on titanium silicalite catalyst. Methanol and water may be present in the reaction. The process includes flashing lower boiling components comprising propylene oxide as vapor from a reaction liquid stream and recycling a slurry of the solvent and the catalyst from the flashing step to the reaction step.